Electrohydraulic valve for controlling operation of an engine cylinder valve

ABSTRACT

An electrically operated valve controls the flow of oil to and from a device that activates and deactivates a cylinder of a multi-cylinder engine. A first valve seat is between an inlet and a workport connected to the device and a second valve seat is between the workport and an outlet. A valve element engages the first valve seat when a solenoid actuator is energized. The valve element and the first valve seat cooperate to allow air to bleed from the inlet through the valve upon starting the engine, but prevent the oil from flowing in that path unless the solenoid actuator is energized. In one version of the valve, the valve element engages the second valve seat when disengaged from the first valve seat. In a second version, another valve element engages the second valve seat when oil flows through the first valve seat.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electrohydraulic valves, and moreparticularly to such valves that control operation of intake and exhaustvalves of a multi-cylinder internal combustion engine to selectivelyactivate and deactivate or otherwise control operation of selectedcylinders.

2. Description of the Related Art

In an effort to improve fuel economy, automobile manufacturers havedevised systems that deactivate selected cylinders of an engine when thefull power produced by all the cylinders is not required. For example,the “V-8-6-4 engine” is able to switch between four, six and eightcylinder operation. The selection of which cylinders to deactivate isdetermined by engine firing order with the desire to keep an even firingorder in the deactivated mode. Several modes of cylinder deactivationare possible. In a bank mode, the multiple cylinders in the same bank ofa V-configuration engine are switched at the same time, whereas eachcylinder is switched independently in the cylinder control mode. A givencylinder is activated and deactivated by controlling the operation ofthe intake valves for that cylinder. By disabling the intake valve orvalves for a given cylinder, the air-fuel mixture does not enter thatcylinder and thus combustion does not occur. The exhaust valve also maybe disabled in a similar manner.

The engine cylinder valve operation is controlled by a solenoidactivated hydraulic valve which governs the flow of pressurized enginelubricating oil to a cylinder valve actuator. When the solenoid valve isenergized, pressurized engine oil is applied from a workport of thatvalve to operate a spring-biased locking pin inside the cylinder valvelifter, which effectively decouples the cam shaft from the cylindervalve. When the solenoid is de-energized, the solenoid valve's workportis connected to the engine oil pan releasing the pressure at thecylinder valve actuator, which results in a spring biasing the lockingpin to activate the intake or exhaust valve. Alternatively, the lockingpin for the cylinder valve lifter can be configured so that energizingand de-energizing the solenoid valve has the opposite effects.

It is desirable to control the switching of the engine cylinder valvesin less than one engine cycle. Therefore, the solenoid valve mustrespond very quickly in order to ensure timely deactivation andreactivation of the engine cylinder valve. Thus, it is desirable thatthe solenoid valve is required to generate as little force as possiblethereby minimizing operating time.

When the engine is turned off, the lubricating oil that was used tocontrol the engine cylinder valves drains into the oil pan and airenters the conduits of the valve control system. Therefore mechanism forbleeding the air from the system upon starting the engine has to beprovided.

Because several solenoid activated hydraulic valves are require, it isdesirable to provide a valve assembly which facilitates positioning andattaching those valves to the engine. In addition the valve assemblyshould be highly immune to vibrations, temperature changes and fluidexposure.

SUMMARY OF THE INVENTION

An electrohydraulic valve for a hydraulic system is provided to controloperation of intake and exhaust valves of a multi-cylinder engine. Theelectrohydraulic valve has a valve body with a bore into which an inlet,an outlet and a workport open. The bore has a first valve seat betweenthe inlet and workport and a second valve seat between the workport andthe outlet. A mechanically unbiased valve element is movably located inthe bore for selectively engaging and disengaging the first valve seatto close communication between the inlet and the workport. The valveelement and first valve seat are so constructed that when the enginestarts, air in the hydraulic system is able to bleed from the inlet pastthe first valve seat regardless of whether the cylinder valve is activeor de-active.

An actuator has an electromagnetic coil into which an armature isslidably received. A stem projects from the armature to selectivelydisengage and move the valve element out of engagement with the firstvalve seat against pressure at the inlet.

In a first embodiment of the electrohydraulic valve, a second valveelement is connected to the armature. The second valve element engagesthe second valve seat to close communication between the workport andthe outlet when the first valve element is disengaged from the firstvalve seat. A spring is incorporated which applies a force that tends tomove the second valve element away from the second valve seat and thestem away from the first valve element. Air in the hydraulic system,when the engine starts, is able to flow from inlet through the firstvalve seat without forcing valve element against the first valve seat.However, more viscous hydraulic oil entering the inlet forces the valveelement against the first valve seat unless the actuator is holding thevalve element away.

In a second embodiment of the electrohydraulic valve, a tubular memberis slidably received within the bore between the inlet and a lip in thebore. The first valve seat is formed on an end of the tubular memberthat faces the workport. The valve element alternately engages the firstand second valve seats. In this version of the valve when themulti-cylinder engine starts, air in the hydraulic system is able toflow from inlet around the tubular member to the outlet while the valveelement engages the first valve seat. Upon exhaustion of air from thehydraulic system, pressure from oil at the inlet forces the tubularmember against the lip of the bore thereby closing a path around thetubular member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an assembly of electrohydraulic valves accordingto the present invention;

FIG. 2 is a side view of the valve assembly;

FIG. 3 is a top view of a base plate in the valve assembly;

FIGS. 4, 5, and 6 are top, side and end views, respectively, of andelectrical lead subassembly incorporated into the electrohydraulic valveassembly;

FIG. 7 is an enlarged side view of a section of the electrical leadsubassembly;

FIG. 8 is an enlarged top view of the section of the electrical leadsubassembly;

FIG. 9 is a cross section view along line 4—4 in FIG. 2 through one ofthe electrohydraulic valves; and

FIG. 10 is a cross section view through another embodiment of anelectrohydraulic valve.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1–3, a valve assembly 10 has a thin, planar baseplate 12 fabricated of metal with three openings 14, 15 and 16 extendingbetween two opposing major surfaces 17 and 18. Three electrohydraulicvalves 21, 22 and 23 are located in the three openings 14, 15 and 16,respectively. The base plate 12 is dimensioned to attach to a manifold25 of an multi-cylinder engine wherein the bodies of the threeelectrohydraulic valves 21–23 that extend beneath the base plate enterapertures in the manifold. Each base plate opening 14–16 is slightlylarger that the outer dimension of electrohydraulic valve enabling thevalve to move freely in two orthogonal axes on a major surface 17 or 18of the base plate 12. As will be described, this loose attachment allowseach electrohydraulic valve to seat itself in the respective manifoldaperture and accommodate dimensional irregularities of the componentswhen the valve assembly 10 is mounted to the engine. A pair of prongs 24project from opposite sides toward the center of each base plate opening14–16. The distance between the prongs 24 is slightly larger than theouter dimension of outer metal cap 26 of the electrohydraulic valve21–23. The edge of the outer cap 26 which abuts the base plate 12 has apair of tabs 28 which project through the opening 14, 15 or 16 and areloosely bend against the underside side of the base plate. Until thevalve assembly 10 is attached to the engine, the tabs 28 do not restrictmovement of the three electrohydraulic valves 21, 22 and 23 with respectto the base plate 12.

An electrical lead frame 30 has a foot 31 with a pin 38 that projectsthrough an aperture 39 to the base plate 12 and has a mounting aperture36 that aligns with a hole 37 in the base plate 12 (see FIG. 3) toreceive a bolt as will be described. The electrical lead frame 30 has aconnector post 32 projecting from the foot 31 away from the base plate12. The lead frame 30 also has a thin, flexible bar 34 that iscantilevered from the foot 31 and connector post 32 along onelongitudinal edge of the base plate 12. The flexible bar 34 is notdirectly connected to the base plate 12. The foot 31, connector post 32and flexible bar 34 are fabricated from plastic that is molded around aset of electrical leads that extends from an electrical connector 35 atthe end of the connector post to pairs of terminals 46–49 adjacent theelectrohydraulic valves 21–23. The electrical connector 35 receives amating connector on an end of a cable that extends from the enginecomputer.

The connection of the lead frame 30 to each electrohydraulic valve 21–23prevents the valves from falling downward through the base plate 12 inFIG. 2. The outwardly projecting pair of tabs 28 prevents eachelectrohydraulic valve 21–23 from passing upward through the base plate12. This holds the valve assembly 10 together prior to being attached toan engine.

With reference to FIGS. 4–6, the set of electrical leads 40 is stampedas a unit from a flat sheet of brass, although other metals may be used.The stamping is then bend into the form illustrated in the drawings. Theresultant structure has four parallel, coplanar conductors 41, 42, 43and 44, which are initially joined together by thin ties 45. The firstconductor 41 is connected in common to all three electrohydraulic valves21–23, while each of the other three conductors 42, 43 and 44 isconnected to only one of the valves. Thus the first conductor 41 hasthree terminals 46, one adjacent each valve location (see FIG. 1). Thesecond conductor 42 has a terminal 47 adjacent the firstelectrohydraulic valve 21 and a terminal 48 of the third conductor 43 isnear the second electrohydraulic valve 22. The fourth conductor 44 has aterminal 49 adjacent the third electrohydraulic valve 23.

Each conductor 41, 42, 43 and 44 is joined to an end of a differentL-shaped leg 50, 51, 52 or 53, respectively, which are in a planeperpendicular to the plane of the conductors. The other ends of theL-shaped legs 50, 51, 52 and 53 are connected to four contacts 54, 55,56 and 57, respectively, which are in a plane perpendicular to theplanes of the L-shaped legs and the conductors.

As seen in FIGS. 4 and 5, the second conductor 42 has a bridge 59 whichcrosses over an arm 41 a of the first conductor 41 that extends to theterminal 46 for the second electrohydraulic valve 22. The details ofthis cross over are shown in the rear view this portion of the set ofelectrical leads 40 in FIG. 7 and also in the enlarged top view in FIG.8. The second conductor 42 has a gap thereby segmenting the conductorinto two aligned sections 42 a and 42 b. The arm 41 a of the firstconductor 41 extends through that gap (see FIG. 5). A pair of U-shapedcouplings 58 each have one end extending from a different section 42 aor 42 b of the second conductor 42. The other ends of the couplings 58are spaced from the plane of the conductors 41–44 and a bridge 59extends between those other ends. In the assembled electrical lead frame30, the plastic of the flexible bar 34 maintains the bridge 59 spacedfrom the conductors 41–44.

Referring again to FIGS. 1 and 2, when the plastic is molded around theset of electrical leads 40, the four parallel, conductors 41–44 areencased in the flexible bar 34, the L-shaped legs 50–53 are in the foot31, and the four contacts 54–57 are in the connector post 32. When themold closes, its elements hold the in the conductors 41–44 in place andsever the ties 45 between the conductors 41, 42, 43 and 44 prior to theplastic being injected into the mold.

The Electrohydraulic Valves

The construction of the first electrohydraulic valve 21 in the assembly10 is illustrated in FIG. 9 with the understanding that the other twovalves 22 and 23 are identical to the first one. The firstelectrohydraulic valve 21 has valve body 60 that fits into the enginemanifold 25 when the valve assembly 10 is mounted on the engine. Thisvalve 21 has a longitudinal bore 62 extending through a valve body 60.An inlet 64 of the bore 62 at valve nose opens into a supply gallery 65of the engine manifold through which pressurized lubricating oil flows,and a transverse outlet 66 provides a path between the bore and a returngallery 67 in the engine manifold that leads to the oil pan. Between theinlet 64 and outlet 66 along the valve body 60 is a workport 68providing a path between the bore and a manifold gallery 69 that leadsto the cylinder valve actuator. A plurality of sealing rings extendexternally around the valve body 60 to engage internal walls of theengine manifold 25.

An annular plug 70 is secured in the opening of the bore 62 and formsthe valve inlet 64. A first valve seat 74 is formed in the bore betweenthe valve inlet 64 and the workport 68. A first valve element 76, in theform of a sphere, is captivated in a chamber 72 of the bore 62 locatedbetween the plug 70 and a first valve seat 74. The first valve element76 is mechanically unbiased and able to move freely in the chamber 72 inresponse to fluid pressure. A second valve seat 78 is formed in the bore62 between the workport 68 and the outlet 66.

A second valve element 80, in the form of a poppet, is slidably receivedwithin the bore 62 of the valve body 60 and selectively engages thesecond valve seat 78 to control fluid flow between the workport 68 andthe outlet 66. A spring 85 biases the second valve element 80 away fromthe second valve seat 78. A stem 82 projects from the second valveelement 80 toward the first valve member. The second valve element 80 isattached to and operated by an armature 86 of a solenoid actuator 84.The second valve element 80, the stem 82, and the armature 86 preferablyare fabricated as a single piece.

The solenoid actuator 84 also includes an electromagnetic coil 88 woundon a bobbin 90 that has a central aperture through which the armature 86extends. A pair of terminals 91 for the electromagnetic coil 88 extendhorizontally outward (see also FIG. 1) and are resistance welded to theterminals 46 and 47 on the lead frame 30. The electromagnetic coil 88and the bobbin 90 are contained within the metal cap 26 which has anopen end closed by a magnetic pole piece 94 and the valve body 60 thatis secured to the cap. The magnetic pole piece 94 has a circular rim 95which fits into the opening of the bore 62 at the interior end of thevalve body 60. This circular rim 95 aids in aligning the solenoidactuator 84 with the body 60 during assembly of the valve 21.

The cap 26 has a vent aperture 96 through which oil that leaks past thearmature escapes from the cap and into the engine. Typically the valveassembly 10 is located beneath the engine valve cover so that theescaping lubricating oil is contained to flow through the engine andinto the oil pan. The metal valve cap 26 has a tongue 98 which extendsfrom one side and is bent around the lead frame 30 to secure thosecomponents together.

FIG. 9 illustrates the first electrohydraulic valve 21 in the energizedstate in which electric current is being applied to the electromagneticcoil 88 of the solenoid actuator 84. This creates a magnetic field thatdrives the armature 86 farther into the valve body 60. This movementforces the second valve element 80 against the first valve seat 78thereby closing a fluid path between the workport 68 and the outlet 66.Motion of the armature 86 also causes the stem 82 to push the firstvalve element 76 away from the first valve seat 74 which opens a pathbetween the inlet 64 and the workport 68. In this state of the firstelectrohydraulic valve 21, pressurized lubricating oil is appliedthrough the workport 68 to the cylinder valve actuator and deactivatesthe engine cylinder valve.

When the electric current is removed from the electromagnetic coil 88,the spring 85 and hydraulic pressure forces the second valve element 80away from engagement with the second valve seat 78. As a result a fluidpath is opened between the workport 68 and the outlet 66. This motionalso moves the stem 82 away from the first valve element 76 which allowsthe pressure at the inlet 64 to move the first valve element intoengagement with the first valve seat 74 thus closing the path betweenthe inlet 64 and the workport 68. This position of the firstelectrohydraulic valve 21 releases the pressure previously applied tothe cylinder valve actuator and activates the associated enginecylinder.

When the engine is turned off, the first electrohydraulic valve 21 isde-energized. The force of the spring 85 moves the second valve element80 away from the second valve seat 78 and the stem 82 away from thefirst valve element 76 thereby releasing any fluid pressure at theworkport 68. Initially pressure at the valve inlet 64 holds the firstvalve element 76 against the first valve seat 74. Eventually the inletpressure decreases to the atmospheric pressure level. When that pressureequalization occurs the first valve element 76 drops away from the firstvalve seat 74 due to gravity and lubricating oil in the passages of theengine drains into the oil pan. This introduces air into the firstelectrohydraulic valve 21 and the galleries of the engine manifold.

When the engine is restarted, the air within the manifold supply galleryis forced to the valve inlet 64 by lubricating oil from the nowoperating oil pump of the engine. Initially all the engine cylinders areactive wherein the first electrohydraulic valve 21 is de-energized sothat the second valve element 80 is away from the second valve seat 78and the stem 82 is disengaged from the first valve element 76. However,the relative low viscosity of the air flowing through the inlet 64 isinsufficient to produce a great enough pressure differential to move thespherical first valve element 76 fully upward against the first valveseat 74. As a result, the air bleeds from the inlet 64 through thesecond valve seat 78 and into the outlet 66 from which the air flows toa chamber underneath the engine valve cover. Some lubricating oil flowspast the first valve seat 74 and displaces air in the gallery connectedto the workport 68. Eventually all the air from the supply gallery isforced through the inlet 64 and the more viscous lubricating oil createsa significantly great pressure differential which applies sufficientforce to move the first valve element 76 against the first valve seat74. Thus air is automatically bled from the hydraulic system. Therefore,the present electrohydraulic valve incorporates a mechanism thatautomatically bleeds air from the hydraulic system for activating anddeactivating the engine cylinders.

FIG. 10 illustrates a second embodiment of an electrohydraulic valve 100according to the present invention and which has valve body 101 with alongitudinal bore 102 extending there through. The valve body 101 has aninlet 104 at an exposed end of the bore 102, a transverse outlet 106,and a transverse workport 108 between the inlet and outlet. A firstvalve seat 110 is formed on a tubular member 111 that is slidablyreceived within the bore between the valve inlet 104 and the workport108. A second valve seat 114 is formed in the bore 102 between theworkport 108 and the outlet 106. A spherical valve element 112 iscaptivated in the bore 102 and selectively engages the first and secondvalve seats 110 and 114 one at a time.

The spherical valve element 112 is operated on by a stem 120 thatprojects from an armature 118 that is part of the solenoid actuator 122.The armature 118 is biased into engagement with the spherical valveelement 112 by a spring 126 and is driven away from the spherical valveelement by the magnetic field produced by an electromagnetic coil 124.The first magnetic pole piece 128 is fixedly secured within a metal cap130 of the solenoid actuator 122 extending into the electromagnetic coil124. Both the first magnetic pole piece 128 and the cap 130 haveapertures 132 and 134 to allow oil that leaks past the armature 118 toescape from the valve 100. The metal cap 130 has an open end that isclosed by a second annular magnetic pole piece 136 and the valve body101 to which the cap is secured.

The metal cap 130 of the solenoid actuator 122 has a tongue 140 whichextends from one side and is bent around the lead frame 30. Electricalterminals 142 of the electromagnetic coil 124 are resistance welded toterminals of the lead frame 30 thereby electrically connecting the valve100 to the engine computer.

In the de-energized state of the electrohydraulic valve 100, the forceof the spring 126 is greater than the force exerted by pressure at theinlet 102. Therefore, the armature 118 is moved downward in the drawingswherein the stem 120 pushes the spherical valve element 112 against thefirst valve seat 110 which in turn slides the tubular member 111 againststops at the inlet 104. In this state, the spherical valve element 112abutting the first valve seat 110 effectively blocks flow of oil fromthe inlet 104. However, oil is able to flow from the workport 108 pastthe stem 120 and armature 118 to the outlet 106. Therefore, pressure isrelieved at the workport 108, thereby causing the cylinder valveactuator to activate the engine cylinder.

When the engine is turned off, the pressure in the hydraulic systemequalizes at the atmospheric pressure level. When this occurs, gravitycauses the tubular member 111 and the spherical valve element 112 todrop against stops at the inlet 104. When the engine is restarted, airin the valve hydraulic system flows into the valve inlet 104 and throughsmall gap between the outer surface of the tubular member 111 and thebore 102. This air flow continues to the valve outlet 106 from which itis exhausted from the system. The relatively low viscosity of the airdoes not create a great enough pressure differential to applysignificant force to move the tubular member 111 away from the inlet104. When lubricating oil, which has a greater viscosity than air,reaches the inlet 104, the tubular member 111 is forced upward against alip 116 in the bore 102 which seals the gap between the tubular memberand the bore. The force of the pressurized oil, that now is applied tothe surface area of the spherical valve element 112 exposed in thecentral opening through the tubular member 111, is insufficient tocounteract the spring force and unseat the valve element from the firstvalve seat 110.

When the electrohydraulic valve 100 is energized, the magnetic fieldproduced by the electromagnetic coil 124 draws the armature upwardagainst the force of spring 126. This action moves the stem 120 awayfrom the spherical valve element 112, which then is forced by the inletoil pressure away from the first valve seat 110 and against the secondvalve seat 114. In this state, pressurized lubricating oil flows fromthe inlet 104 through the workport 108 to deactivate the engine cylindervalve. The spherical valve element 112 abutting the second valve seat114 prevents oil from flowing to the outlet 106.

Fabricating of the Valve Assembly

Prior to mounting each electrohydraulic valve 21–23 on the base plate12, the tongue 98 of the metal valve cap 26 has an large upper opening.The valve assembly 10 is constructed by inserting the threeelectrohydraulic valves 21–23 upward into the respective openings 14–16in the base plate 12 until the tabs 28 abut the underside of the baseplate. The relatively large size of the openings 14–16 able the valves21–23 to move along the two orthogonal axes of the plane of the baseplate 12.

Next the flexible bar 34 of the electrical lead frame 30 is insertedbetween the main part of each valve's cap 26 and the tongue 98. As thisoccurs the pin 38 on the lead frame foot 31 passes into the aperture 39in the base plate 12. The tips of the tongues 98 then are bend over theupper edge of the flexible bar 34 to secure the three electrohydraulicvalves 21–23 to the electrical lead frame 30. At this point theelectrohydraulic valves 21–23 are captivated in the assembly by theconnection to the lead frame 30 and the outwardly projecting valve tabs28, thereby holding the valve assembly 10 together prior to beingattached to an engine.

When the valve assembly is mounted on the engine manifold 25, the bodies60 of the three electrohydraulic valves 21–23 are inserted into separateopenings in the manifold. The pin 38 on the lead frame connector post 32that projects through the base plate 12 enters a locating aperture inthe manifold to position the base plate. Bolts 148 are placed throughapertures 150 in the base plate 12 and into threaded holes in themanifold 25. As the bolts 148 are tightened, the electrohydraulic valvesare pushed farther into the manifold openings. The loose engagement ofthe valves with the base plate 12 allows each valve to move with respectto the base plate and properly seat in the respective opening. Thecantilevered bar 34 of the lead frame 30 flexes to allow each valve21–23 to move in an arc with respect to the connector post 32 andthereby adjust the valve's position for dimensional irregularitiesbetween the valve openings and the bolt holes in the manifold. When thebolts are fully tightened, the tabs 28 on electrohydraulic valves 21–23are clamped between the base plate 12 and the manifold 25 preventingfurther movement of the valves, which thereby are secured in place.

Furthermore, vibration produced by engine operation is absorbed by thelead frame 30 flexing along is length and is not concentrated at theelectrical connections between the valves and the lead frame. Thisdistribution of the vibrational motion significantly reduces fatiguewhich otherwise would occur at these joints.

The foregoing description was primarily directed to a preferredembodiments of the present invention. Although some attention was givento various alternatives within the scope of the invention, it isanticipated that one skilled in the art will likely realize additionalalternatives that are now apparent from disclosure of embodiments of theinvention. Accordingly, the scope of the invention should be determinedfrom the following claims and not limited by the above disclosure.

1. An electrohydraulic valve for a hydraulic system which controlsoperation of a cylinder valve of a multi-cylinder engine, theelectrohydraulic valve comprising: a valve body having a bore into whichopen an inlet, an outlet and a workport, with a first valve seat formedin the bore between the inlet and the workport, and a second valve seatformed in the bore between the workport and the outlet; a first valveelement movable in the bore in a mechanically unbiased manner andselectively engaging and disengaging the first valve seat to closecommunication between the inlet and workport, wherein when themulti-cylinder engine starts air in the hydraulic system is allowed tobleed from the inlet past the first valve seat regardless of whether thecylinder valve is active or de-active; and an actuator having anelectromagnetic coil, an armature is slidably received in theelectromagnetic coil, and a stem projecting from the armature to engageand move the first valve element within the bore.
 2. Theelectrohydraulic control valve as recited in claim 1 further comprisinga second valve element connected to the armature and selectivelyengaging the second valve seat when the first valve element isdisengaged from the first valve seat.
 3. The electrohydraulic controlvalve as recited in claim 2 further comprising a spring applying a forcewhich tends to move the second valve element away from the second valveseat.
 4. The electrohydraulic control valve as recited in claim 2wherein the armature, the second valve element and the stem are formedas a single piece.
 5. The electrohydraulic control valve as recited inclaim 1 further comprising a cap enclosing the electromagnetic coil andhaving a vent aperture through which oil that leaks between theelectromagnetic coil and the armature exhausts from the cap.
 6. Theelectrohydraulic control valve as recited in claim 1 further comprisinga pole piece at one end of the electromagnetic coil and having a rimwhich fits within the bore of the valve body to locate the actuator withrespect to the valve body.
 7. The electrohydraulic control valve asrecited in claim 1 wherein the first valve element selectively engagesthe second valve seat upon disengaging from the first valve seat.
 8. Theelectrohydraulic control valve as recited in claim 7 wherein the firstvalve seat is formed on a tubular member that is slidably receivedwithin the bore between the inlet and the workport.
 9. Theelectrohydraulic control valve as recited in claim 8 wherein the valvebody has a lip in the bore to restrict motion of the tubular membertoward the workport.
 10. The electrohydraulic control valve as recitedin claim 7 wherein the stem urges the valve element against the firstvalve seat.
 11. The electrohydraulic control valve as recited in claim 7further comprising a spring which applies a force that urges the stemtoward engagement with the valve element.
 12. An electrohydraulic valvefor a hydraulic system which controls operation of a cylinder valve of amulti-cylinder engine, the electrohydraulic valve comprising: a valvebody having a bore into which open an inlet, an outlet and a workport,the valve body further including a first valve seat between the inletand the workport and a second valve seat between the workport and theoutlet; a first valve element movable in the bore in a mechanicallyunbiased manner and selectively engaging and disengaging the first valveseat to close communication between the inlet and workport, when themulti-cylinder engine starts the valve element allowing air in thehydraulic system to bleed from the inlet through the first valve seatregardless of whether the cylinder valve is active or de-active; anactuator attached to the valve body and having an electromagnetic coilwithin which an armature is slidably received; a second valve elementconnected to the armature and selectively engaging and disengaging thesecond valve seat to close communication between the workport and theoutlet; a spring applying a force which tends to move the second valveelement away from the second valve seat; and a stem projecting from thearmature to selectively engage and move the first valve element awayfrom the first valve seat.
 13. The electrohydraulic control valve asrecited in claim 12 wherein the armature, the second valve element andthe stem are formed as a single piece.
 14. The electrohydraulic controlvalve as recited in claim 12 further comprising a cap enclosing theelectromagnetic coil and having a vent aperture through which oil thatleaks between the electromagnetic coil and the armature exhausts fromthe cap.
 15. The electrohydraulic control valve as recited in claim 12further comprising a pole piece at one end of the electromagnetic coiland having a rim which fits within the bore of the valve body to locatethe actuator with respect to the body.
 16. An electrohydraulic valve fora hydraulic system which controls operation of a cylinder valve of amulti-cylinder engine, the electrohydraulic valve comprising: a valvebody having a bore into which open an inlet, an outlet and a workport,and having a lip formed in the bore between the inlet and the workport;a tubular member that is slidably received within the bore between theinlet and the lip of the bore, and having an end facing the workportwith a first valve seat formed on that end; wherein a second valve seatis formed in the bore between the workport and the outlet; a valveelement mechanically unbiased and movable in the bore between engagementwith first valve seat and engagement with the second valve seat; whereinwhen the multi-cylinder engine starts, air in the hydraulic system flowsfrom the inlet around the tubular member while the valve element engagesthe first valve seat; and an actuator having an electromagnetic coil, anarmature slidably received in the electromagnetic coil, and a stemprojecting from the armature to move the valve element away from thesecond valve seat and into engagement with the first valve seat.
 17. Theelectrohydraulic control valve as recited in claim 16 wherein uponexhaustion of air from the hydraulic system, oil flowing through theinlet forces the tubular member against the lip of the bore therebyclosing a path around the tubular member.
 18. The electrohydrauliccontrol valve as recited in claim 16 further comprising a spring whichapplies a force that urges the stem toward engagement with the valveelement.
 19. The electrohydraulic control valve as recited in claim 16further comprising a cap enclosing the electromagnetic coil and having avent aperture through which oil that leaks between the electromagneticcoil and the armature exhausts from the cap.
 20. The electrohydrauliccontrol valve as recited in claim 16 further comprising a pole piece atone end of the electromagnetic coil and having a rim which fits withinthe bore of the valve body to locate the actuator with respect to thevalve body.